1. Field of the Invention
The present invention relates to an active matrix-type display apparatus, for example, a display apparatus such as an organic electroluminescence (EL) display apparatus and an information processing apparatus using the same.
2. Description of the Related Art
A flat display apparatus formed of current driven type light emitting elements such as EL elements has pixels arranged in plural rows and columns and commonly connected to scanning lines on a row basis and data lines on a column basis. Such a flat display apparatus generally uses a matrix driving in which a row scanning circuit selects each scanning line and at the same time a column scanning circuit applies a predetermined display signal to each data line to cause pixels in the selected row to be subjected to a predetermined display.
A current setting method is known as a method of driving an active matrix-type display apparatus formed using EL elements. The current setting method writes data current into a pixel circuit and controls current flowing into an EL element based on the written data current to adjust light emission intensity of each pixel. An active matrix EL display device using the current setting method is disclosed in U.S. Pat. No. 6,373,454.
FIG. 13 illustrates a schematic configuration of the EL display apparatus. The display apparatus includes a column current control circuit 101, scanning line driving circuit 102 and pixel circuit 103.
FIG. 14 illustrates an example of a pixel circuit with an EL element. Reference characters P1 and P2 denote scanning signal lines. Current data “Idata” being an information signal is input into an information line. The anode of the EL element (“A” in FIG. 14) is connected to the drain terminal of a thin film transistor (TFT) M4 and the cathode thereof (“K” in FIG. 14) is connected to a ground potential CGND. The pixel circuit further includes p-type thin film transistors (PMOS transistors) M1, M2 and M4 and an n-type thin film transistor (NMOS transistors) M3.
The following describes the operation of the pixel circuit in FIG. 14.
When the current data Idata is input, a HIGH level signal is input into the scanning signal line P1 and a LOW level signal is input into the scanning signal line P2. Then, the transistors M2 and M3 are turned on and the transistor M4 is turned off. At this point, the transistor M4 is not in a conductive state, which causes a current not to flow into the EL element. The current data Idata generates a voltage according to the current driving ability of the transistor M1 across a capacitance C1 arranged between the gate terminal of the transistor M1 and the power source potential Vcc. Thus, a current, which is caused to flow in the EL element during the light emission period of the EL element, is held as the gate voltage of the transistor M1.
When a current needs to be supplied to the EL element, a LOW level signal is input into the scanning signal line P1 and a HIGH level signal into the scanning signal line P2. At this point, the transistor M4 is turned on and the transistors M2 and M3 are turned off. Since the transistor M4 is in a conductive state, by a voltage generated across the capacitance C1, a current according to the current driving ability of the transistor M1 is supplied to the EL element. This causes the EL element to emit light with brightness according to the supplied current.
The active matrix-type display apparatus with the above configuration has a problem with display blur having tailing effect.
The display blur having tailing effect occurs when the maximum current and the minimum current are caused to flow into a certain information line in this order. In this case, a little larger current is programmed for a pixel which should be programmed with the minimum current, thereby causing the EL element to emit light with a little higher brightness.
On the other hand, the display blur having tailing effect also occurs when the minimum and the maximum current are caused to flow into a certain information line in this order. In this case, a little smaller current is programmed for a pixel which should be programmed with the maximum current, thereby causing the EL element to emit light with a little lower brightness.
This is partly because the output of the column current control circuit 101 attempts to cause current Idata to flow according to an information signal, however, parasitic capacitance and resistance existing in the information line round a current waveform, which insufficiently accumulates charges into the capacitance C1.